es.array-buffer.slice.js

'use strict';
var $ = require('../internals/export');
var fails = require('../internals/fails');
var ArrayBufferModule = require('../internals/array-buffer');
var anObject = require('../internals/an-object');
var toAbsoluteIndex = require('../internals/to-absolute-index');
var toLength = require('../internals/to-length');
var speciesConstructor = require('../internals/species-constructor');

var ArrayBuffer = ArrayBufferModule.ArrayBuffer;
var DataView = ArrayBufferModule.DataView;
var nativeArrayBufferSlice = ArrayBuffer.prototype.slice;

var INCORRECT_SLICE = fails(function () {
  return !new ArrayBuffer(2).slice(1, undefined).byteLength;
});

// `ArrayBuffer.prototype.slice` method
// https://tc39.github.io/ecma262/#sec-arraybuffer.prototype.slice
$({ target: 'ArrayBuffer', proto: true, unsafe: true, forced: INCORRECT_SLICE }, {
  slice: function slice(start, end) {
    if (nativeArrayBufferSlice !== undefined && end === undefined) {
      return nativeArrayBufferSlice.call(anObject(this), start); // FF fix
    }
    var length = anObject(this).byteLength;
    var first = toAbsoluteIndex(start, length);
    var fin = toAbsoluteIndex(end === undefined ? length : end, length);
    var result = new (speciesConstructor(this, ArrayBuffer))(toLength(fin - first));
    var viewSource = new DataView(this);
    var viewTarget = new DataView(result);
    var index = 0;
    while (first < fin) {
      viewTarget.setUint8(index++, viewSource.getUint8(first++));
    } return result;
  }
});